Observation of Magnetic Edge State and Dangling Bond State on Nanographene in Activated Carbon Fibers

TL;DR

This study uses NEXAFS to reveal magnetic edge states and dangling bond states in nanographene within activated carbon fibers, showing how fluorination influences their electronic and magnetic properties.

Contribution

It provides direct spectroscopic evidence of both edge and dangling bond states coexisting in fluorinated nanographene, linking electronic structure to magnetic behavior.

Findings

Edge states observed below the conduction peak in pristine ACFs.

Fluorination introduces a peak associated with dangling bonds.

The intensity of the dangling bond peak correlates with spin concentration.

Abstract

The electronic structure of nanographene in pristine and fluorinated activated carbon fibers (ACFs) have been investigated with near-edge x-ray absorption fine structure (NEXAFS) and compared with magnetic properties we reported on previously. In pristine ACFs in which magnetic properties are governed by non-bonding edge states of the \pi-electron, a pre-peak assigned to the edge state was observed below the conduction electron {\pi}* peak close to the Fermi level in NEXAFS. Via the fluorination of the ACFs, an extra peak, which was assigned to the \sigma-dangling bond state, was observed between the pre-peak of the edge state and the {\pi}* peak in the NEXAFS profile. The intensities of the extra peak correlate closely with the spin concentration created upon fluorination. The combination of the NEXAFS and magnetic measurement results confirms the coexistence of the magnetic edge states of \pi-electrons and dangling bond states of \sigma-electrons on fluorinated nanographene sheets.